1. Field
Methods and apparatuses consistent with exemplary embodiments relate to an imaging optical system for a three-dimensional (3D) image acquisition apparatus, and a 3D image acquisition apparatus including the imaging optical system, and more particularly, to an imaging optical system having a decreased size and a 3D image acquisition apparatus including the imaging optical system so that the size of the 3D image acquisition apparatus may be decreased.
2. Description of the Related Art
As the demand for 3D display apparatuses has increased, the use of and request for three-dimensional (3D) contents have also increased. Accordingly, 3D image acquisition apparatuses such as 3D cameras for producing 3D contents have been developed. A 3D camera should acquire general two-dimensional (2D) color image information along with depth information via one photographing operation.
The depth information regarding a distance between surfaces of a target object and the 3D camera may be obtained by a stereo vision method using two cameras or by a triangulation method using structured light and a camera. However, as the distance from the target object is increased, the accuracy of the depth information substantially deteriorates when the aforementioned methods are used. Also, the depth information varies with the states of the surfaces of the target object, and thus, it is difficult to acquire accurate depth information when these methods are used.
In order solve these problems, a Time-of-Flight (TOF) method has been developed. In the TOF method, illumination light is irradiated to a target object, and then an optical flight time until light reflected from the target object is received by a light receiving unit is measured. The illumination light has a particular wavelength (e.g., a near infrared ray of 850 nm) and is irradiated to the target object by an illuminating optical system including a light-emitting diode (LED) or a laser-diode (LD), and light that has the same wavelength and is reflected from the target object is received by the light receiving unit. Thereafter, a series of processes in which the received light is modulated by using a modulator having a known gain waveform are performed to extract depth information. Various TOF methods using a predetermined series of optical processes have been introduced.
In general, a 3D camera using a TOF method includes an illuminating optical system for emitting illumination light to acquire depth information, and an imaging optical system for acquiring an image of a target object. The imaging optical system generates a general color image by sensing visible light reflected from the target object and simultaneously generates a depth image only having depth information by sensing illumination light reflected from the target object. For this purpose, the imaging optical system may separately include an object lens and an image sensor for visible light, and an object lens and an image sensor for illumination light (i.e., a two-lens and two-sensor structure). However, in the two-lens and two-sensor structure, a color image and a depth image have different fields of view, and thus, a separate process is required to accurately match the two images. Accordingly, a size of the 3D camera and the manufacturing costs are increased.
Thus, a 3D camera having one common object lens and two image sensors (i.e., a one-lens and two-sensor structure) has been developed. However, even in the one-lens and two-sensor structure, there remains a need to prevent volume and weight increases of an imaging optical system and the 3D camera and also an increase of the manufacturing costs.